2 under 2

So, being that I'm 21 weeks along today, I am officially starting to freak out about the prospect of have to children under 2 years old. It's not the mechanics of having a newborn. It's the reaction of my oldest that I'm worried about. She is wonderful but SO attached to mommy. It's very sweet and I love it but I don't think she will like the compromise of sharing me with another little person. Ahhhhh!